The invention relates to a method and a measuring apparatus for determining gas properties by correlation.
The (natural) gas composition and thus the gas quality will fluctuate in future to a higher extent and more frequently than today as a result of new sources of origin (biogas, liquefied natural gas from all areas of the world, hydrogen from the exploitation of excess current in alternative power generation) and will therefore have different effects in gas application processes, which may also include such that have a negative effect. With knowledge of the relevant gas properties on site, the processes could be adjusted to the varying gas quality in order to ensure optimal and secure operation. In connection with gas properties that are relevant in this context, this includes for example the Wobbe index for burner controllers, the air to fuel ratio in power generation plants such as industrial furnaces and fuel cells, the methane number for gas motors, or the calorific value for billing the purchased energy quantity. These gas properties can often only be measured directly at great expense, so that an on-site determination is usually not economical.
A method and a measuring apparatus for determining physical gas properties is known from European Patent Application EP 2 806 271 A1, in which a desired gas property is determined by means of correlation from several basic physical quantities of a gas that can be determined in a simple manner such as the thermal conductivity. An on-site determination of the desired gas property is then also enabled with this simple measuring apparatus. Although a potential correlation function is mentioned in equation 16 of the mentioned patent application, the precision which applies to this correlation for the gas mixture shown in FIG. 4 is not stated.